How to use WSO2 Class Mediator in WSO2 ESB

The Class Mediator creates an instance of a custom-specified class and sets it as a mediator. If any properties are specified, the corresponding setter methods are invoked once on the class during initialization.

Use the Class mediator for user-specific, custom developments only when there is no built-in mediator that already provides the required functionality. 

The syntax of Class Mediator in ESB

<class name="class-name">

   <property name="string" value="literal">

   </property>
</class>




Creating a Class Mediator




lets use the Eclipse WSO2 Developer Studio

Create a New Mediator project by selecting

File --> New --> project --> Mediator Project

Now you have class mediator by extending the AbstractMediator class. Then you need to implement the mediate methods

Sample class mediator implementation is as follows.

package lk.harshana;

import org.apache.synapse.MessageContext; 
import org.apache.synapse.mediators.AbstractMediator;

public class TestMediator extends AbstractMediator { 

 private String variable1;
 private String variable2;
 
 public boolean mediate(MessageContext mc) { 
  System.out.println("===========Starting class mediator==========");
  
  System.out.println("variable1 : " + variable1);
  System.out.println("variable1 : " + variable2);
  
  String prop1 = (String) mc.getProperty("property1");
  int prop2 = (Integer) mc.getProperty("property2");
  
  System.out.println("prop1 : " + prop1);
  System.out.println("prop2 : " + prop2);
  
  int prop3 = (Integer) mc.getProperty("property3");
  
  int calc = add(prop2, prop3);
  
  System.out.println("calc value : " + calc);
  
  mc.setProperty("calc", calc);
  
  System.out.println("=========== ending class mediator===========");
  return true;
 }
 
 private int add(int x, int y) {
  return x + y;
 }
 
 public String getVariable1() {
  return variable1;
 }

 public void setVariable1(String variable1) {
  this.variable1 = variable1;
 }

 public String getVariable2() {
  return variable2;
 }

 public void setVariable2(String variable2) {
  this.variable2 = variable2;
 }
 
}

Now you need to use this in proxy service. So I have created a proxy service to use the class mediator

<?xml version="1.0" encoding="UTF-8"?>

<proxy name="SampleProxy" startOnLoad="true" transports="http https"

 xmlns="http://ws.apache.org/ns/synapse">

 <target>

  <inSequence>

   <log level="custom">

    <property name="start log" value="Proxy Started" />

   </log>

   <property name="property1" value="welcome to class mediator test" type="STRING"/>

   <property name="property2" value="10" scope="default" type="INTEGER"/>

   <property name="property3" value="5" scope="default" type="INTEGER" />

   <class name="lk.harshana.TestMediator">

    <property name="variable1" value="variable 1 value" />

    <property name="variable2" value="variable 2 value" />

   </class>

   <log>

    <property name="calc" expression="$ctx:calc" />

   </log>

  </inSequence>

  <outSequence />

  <faultSequence />

 </target>

</proxy>

You will see the following log in the console

[2018-09-13 15:21:07,127]  INFO - LogMediator start log = Proxy Started
===========Starting class mediator==========
variable1 : variable 1 value
variable1 : variable 2 value
prop1 : welcome to class mediator test
prop2 : 10
calc value : 15
=========== ending class mediator===========
[2018-09-13 15:21:07,129]  INFO - LogMediator To: /services/SampleProxy.SampleProxyHttpSoap12Endpoint, WSAction: urn:mediate, SOAPAction: urn:mediate, MessageID: urn:uuid:0aa5a19e-5e05-49a4-a52e-52a5b1d4351c, Direction: request, calc = 15